Interlocking assembly and method of making same

ABSTRACT

A method of interlocking two elements comprises providing an inner element, an outer element capable of surrounding the inner element and locating at least part of the inner element therein. At least the internal dimensions of said outer element are caused to decrease whereby an internal surface thereof is pressed against said inner element to define cooperating surfaces. At least one of said cooperating surfaces is provided with longitudinal splines and thus is sufficiently hard to produce complementary splines in the other cooperating surface. Also, at least one of said cooperating surfaces is provided with a surface interruption extending across the direction of said splines, and being sufficiently hard and suitably shaped produces a complementary interruption in the other cooperating surface. Hence the assembled elements are secured against both longitudinal and rotational relative displacement.

Unite States Patent [191 Witsenhausen-Adelman INTERLOCKING ASSEMBLY AND METHOD (11F MAKING SAME [22] Filed: Jan. 8, 1971 [21] Appl. No.: 105,045

2,569,275 9/1951 Baker 29/517 X 3,572,779 3/1971 Dawson 287/109 X FOREIGN PATENTS OR APPLICATIONS 232,328 4/1925 Great Britain 287/109 Primary Examiner-Charlie T. Moon Attorney-Young & Thompson [5 7] ABSTRACT A method of interlocking two elements comprises providing an inner element, an outer element capable of surrounding the inner element and locating at least part of the inner element therein. At least the internal dimensions of said outer element are caused to decrease whereby an internal surface thereof is pressed against said inner element to define cooperating surfaces. At least one of said cooperating surfaces is provided with longitudinal splines and thus is sufficiently hard to produce complementary splines in the other cooperating surface. Also, at least one of said cooperating surfaces is provided with a surface interruption extending across the direction of said splines, and being sufficiently hard and suitably shaped produces a complementary interruption in the other cooperating surface. Hence the assembled elements are secured against both longitudinal and rotational relative displacement.

8 Claims, 2 Drawing Figures INTERLOCKING ASSEMBLY AND METHOD OF MAKING SAME This invention concerns an assembly of interlocking elements, in particular of a kind wherein an element such as a rod is held within another such as a tube.

Assemblies have long been known wherein a rod is secured, within a tube through interlocking or complementary longitudinal splines embossed on the outer surface of the internal element and the inner surface of the external element. A torsional force applied to one of the elements is then transmitted directly to the other element with no relative rotation of the two elements.

As assembly of this type does not however oppose any axial stresses since the splines of the two elements can still slide relative to each other;

In" one aspect the present invention provides a method of interlocking two elements comprising:

providing an inner element;

providing an outer element capable of surrounding the inner element and locating at least part of the inner element therein;

causing at least the internal dimensions of said outer element to decrease whereby an internal surface thereof is pressed against said inner element to define cooperating surfaces;

at least one of said cooperating surfaces being provided with longitudinal splines and being sufficiently hard to produce complementary splines in the other cooperating surface;

at least one of said cooperating surfaces being provided with a surface interruption extending across the direction of said splines, and being sufficiently hard and suitably shaped to produce a complementary interruption in the other cooperating surface;

whereby the assembled elements are secured against both longitudinal and rotational relative displacement.

This assembly of two elements can oppose axial forces as well as torsional forces. Optionally, the surface interruption may be a groove and form a complementary tin, or vice versa.

Such a groove preferably extends completely around one surface of the inner element, and may advantageously be helical.

In another aspect the invention provides an assembly of an inner element and a surrounding outer element which are pressed together to define cooperating surfaces at least one of said cooperating surfaces being provided with longitudinal splines and being sufficiently hard to produce complementary splines in the other cooperating surface;

at least one of said cooperating surfaces being provided with a surface interruption extending across the direction of said splines, and being sufficiently hard and suitably shaped to produce a complementary interruption in the other cooperating surface;

whereby the assembled elements are secured against both longitudinal and rotational relative displacement.

Compression may be carried out using any conventional method, including heat. The relative hardness of the two materials can optionally be chosen so that one can be distorted by a pressure. For example, one or both elements may be metal.

Many modified forms can be visualised. The projection or depression can be previously formed and orientated, and only the splines will be engendered during the process. Alternately the projection can be engendered on compressing the external element on toand into a depression in the element surface. I p

The projection can be on either of the two surfaces, and likewise the splines. t

The splines can similarly be pre formed but here there might be distortion when the compressing process is taking place.

This process also increases the wall thickness of the external element abreast of the joint, i.e., in the part of this external element which is particularly effected by the stresses.

A form of embodiment of the assembly according to the invention is described hereinafter by way of nonlimiting example with reference to the accompanying drawing which illustrates the assembly ready for use:

FIG. 1 is a view in axial section of this assembly.

FIG. 2 is a view in section along IIII of FIG. 1.

FIG. 1 illustrates a rod 1 which has engraved longitudinal splines 2 and a helical groove 3 on one end. The end of a tube 4 is constricted over this rod whereby the tube has splines of a shape and size corresponding to,

time a helical fin 6 is formed in the groove 3.

To-produce this assembly one can slide an intially cylindrical tube 4 over, and narrow this tube down radially on to the end of element 1. This constricting action forms the splines 5 and the fin 6 on the inner side of the tube 4.

The splines 2 and 5 ensure a joint of the elements 1 and 4 which opposes torsional movement. The interengagement of fin 6 and groove 3 enables the assembly to oppose axial forces.

A force exerted axially on the assembly tends to cause the tube 4 and the element 1 to turn relative to each other around their. comm-on longitudinal axis, owing to the helical form of the groove and the tin. This turning is opposed by the splines 2 and 5 and the axial force is partly transmitted to the splines rather than being borne exclusively by groove and tin. Increase of strain on the groove. and fin can thus be brought below an unacceptable limit and prevent their deformation.

It is evident that this invention should not be considered as being limited to the forms of embodiment described and illustrated, but as covering also all their modified forms.

What I claim is:

1. A method of interlocking two elements comprising:

providing an inner element;

providing an outer element capable of surrounding the inner element and locating at least part of the inner element therein;

causing at least the internal dimensions of said outer element to decrease whereby an internal surface thereof is pressed against said inner element to define cooperating surfaces;

at least one of said cooperating surfaces being provided with longitudinal splines and being sufficiently hard to produce complementary splines in the other cooperating surface;

at least one of said cooperating surfaces being provided with a helicoidal surface interruption extending across the direction of said splines and deeper than said splines, and being sufficiently hard and suitably shaped to produce a complementary interruption in the other cooperating surface;

whereby the assembled elements are secured against both longitudinal and rotational relative displacement. 2. A method of interlocking two elements, comprising:

providing a rod-like inner element; providing a tubular outer element and locating at least part of the rod-like element therein;

compressing the tubular outer element over the rodlike inner element whereby the internal surface thereof is pressed against said inner element to define .cooperating surfaces;

the cooperating inner element surface being provided with longitudinal splines and with at least one helicoidal surface interruption extending across the splines and deeper than said splines, and being sufficiently hard and suitably shaped to produce a complementary interruption in the cooperating out element internal surface;

whereby the assembled elements are secured against both longitudinal and rotational displacement.

3. A process as claimed in claim 1 wherein the surface interruption is a groove and forms a complementary fin.

4. A process as claimed in claim 1 wherein the surface interruption is a projection and forms a complementary groove.

5. A process as claimed in claim 3 wherein the groove extends completely around one surface of the inner element.

6. An assembly of an inner element and a surrounding outer element which are pressed together to define cooperating surfaces with at least one of said cooperating surfaces being provided with longitudinal splines and being sufficiently hard to produce complementa splines in the other cooperating surface;

at least one of said cooperating surfaces being provided with a surface helicoidal interruption extending across the direction of said splines and deeper than said splines, and being sufficiently hard and suitably shaped to produce a complementary interruption in the other cooperating surface;

whereby the assembled elements are secured against both longitudinal and rotational relative displacement.

7. An assembly as claimed in claim 6, said interruption being a helicoidal groove that extends continuously in a plurality of turns about said inner element and that interrupts said splines thereby to divide each of said splines into a plurality of longitudinally aligned portions.

8. An assembly as claimed in claim 7, said groove having a width greater than the width of a said spline. 

1. A method of interlocking two elements comprising: providing an inner element; providing an outer element capable of surrounding the inner element and locating at least part of the inner element therein; causing at least the internal dimensions of said outer element to decrease whereby an internal surface thereof is pressed against said inner element to define cooperating surfaces; at least one of said cooperating surfaces being provided with longitudinal splines and being sufficiently hard to produce complementary splines in the other cooperating surface; at least one of said cooperating surfaces being provided with a helicoidal surface interruption extending across the direction of said splines and deeper than said splines, and being sufficiently hard and suitably shaped to produce a complementary interruption in the other cooperating surface; whereby the assembled elements are secured against both longitudinal and rotational relative displacement.
 2. A method of interlocking two elements, comprising: providing a rod-like inner element; providing a tubular outer element and locAting at least part of the rod-like element therein; compressing the tubular outer element over the rod-like inner element whereby the internal surface thereof is pressed against said inner element to define cooperating surfaces; the cooperating inner element surface being provided with longitudinal splines and with at least one helicoidal surface interruption extending across the splines and deeper than said splines, and being sufficiently hard and suitably shaped to produce a complementary interruption in the cooperating out element internal surface; whereby the assembled elements are secured against both longitudinal and rotational displacement.
 3. A process as claimed in claim 1 wherein the surface interruption is a groove and forms a complementary fin.
 4. A process as claimed in claim 1 wherein the surface interruption is a projection and forms a complementary groove.
 5. A process as claimed in claim 3 wherein the groove extends completely around one surface of the inner element.
 6. An assembly of an inner element and a surrounding outer element which are pressed together to define cooperating surfaces with at least one of said cooperating surfaces being provided with longitudinal splines and being sufficiently hard to produce complementary splines in the other cooperating surface; at least one of said cooperating surfaces being provided with a surface helicoidal interruption extending across the direction of said splines and deeper than said splines, and being sufficiently hard and suitably shaped to produce a complementary interruption in the other cooperating surface; whereby the assembled elements are secured against both longitudinal and rotational relative displacement.
 7. An assembly as claimed in claim 6, said interruption being a helicoidal groove that extends continuously in a plurality of turns about said inner element and that interrupts said splines thereby to divide each of said splines into a plurality of longitudinally aligned portions.
 8. An assembly as claimed in claim 7, said groove having a width greater than the width of a said spline. 